Hi,
Yes I have used Ventomat. They are a valve that I recommend for water and wastewater service. I have used them in situations to redcue pressure transients in systems with good effect. The installtaion is more difficult than the conventional air valve as to fit an isolation valve and the increased height of the ventomat requires the pipeline to be at a lower level otherwise the valve pit will be aboveground.
The valve is simplicitiy in itself with no lever arms etc. But it delivers the benefit of being able to have multiple orifices to provide surge mitigation.
They have some science and testing behind them whereas I find other more conventional air valve manufacturers generallly make "shapes". When you ask them a technical question they have little idea of the kinetics behind their product.
The original designers of the kinetic air valve, Glenfield and Kennedy of Scotland, have moderniosed their design and they offer similar performance.